CAPE CANAVERAL, Fla. — Mars has teased the imagination since early astronomers discovered that it doesn’t flicker. It glows red as it moves forward and backward in odd, yet predictable, patterns. It was noted in the records of Babylonian, Chinese and Mayan stargazers, and it has figured prominently in ancient mythology.

Science editor Alan Boyle's blog: "Astronaut Abby" is at the controls of a social-media machine that is launching the 15-year-old from Minnesota to Kazakhstan this month for the liftoff of the International Space Station's next crew.

Galileo developed the science of astronomy with his invention of the telescope, and as knowledge of our planetary neighbor grew, Mars appeared to bear a strange kinship to Earth. Astronomers determined that it had close to a 24-hour day and the appearance of an atmosphere, and some even speculated that it harbored intelligent life.

As telescopes improved, observers learned that Mars had two moons, a polar cap and a curious array of surface features — the notorious canali, described by Italy's Giovanni Schiaparelli in 1877.

We Earthlings have sent robots to study Mars' surface many times over the past three decades. Last month, NASA announced new findings: If life ever existed on Mars, the longest-lasting habitats were
most likely below the Red Planet’s surface
.

The new interpretation comes from years of mineral-mapping data, covering more than 350 sites on Mars examined by European and NASA spacecraft. The study suggests that Martian environments with abundant liquid water existed only during short episodes. These episodes occurred toward the end of hundreds of millions of years during which warm water interacted with subsurface rocks. If the research holds up, it's plausible to think that life in some form could have existed back then.

“Our interpretation is a shift from thinking that the warm, wet environment was mostly at the surface to thinking it was mostly in the subsurface, with limited exceptions,” said Johns Hopkins University's Scott Murchie, principal investigator for the CRISM spectrometer on NASA's Mars Reconnaissance Orbiter.

Murchie said that one of the exceptions might be Gale Crater, the landing site for NASA’s $2.5 billion Mars Science Laboratory mission. A car-sized rover named Curiosity is on its way to land in August near the foot of a layered mountain inside the crater. Layers of this mountain contain water-formed minerals, and the rover will travel for miles investigating the alluvial fan of water-carried sediments. NASA hopes the mission will help experts figure out how future humans could live on the Martian landscape.

The question is, can NASA afford to think about sending humans to Mars when the space agency is at what are arguably the most perplexing crossroads in its 53 years of existence?

NASA is busy turning over many of its routine operations in low Earth orbit to commercial partners, while setting its sights on what America’s greatest exploration arm should be doing.

Open Road Integrated Media

"Moon Shot" recounts the story of the early space effort. NBC News correspondent Jay Barbree has updated the book, written with astronauts Alan Shepard and Deke Slayton as co-authors, for the 50th anniversary of the first U.S. and Soviet spaceflights.

Co-authors Alan Shepard and Deke Slayton were at the very heart of America’s efforts to tame space. No one was more qualified to recount the victories won and the defeats endured by a small but remarkable group of humans who took aim at outer space. And no one is more qualified to update this seminal work than NBC News correspondent Jay Barbree, the only journalist to cover every spaceflight flown by astronauts from Cape Canaveral.

Here's how NASA's deputy administrator, Lori Garver, described the situation this month: "Our commercial partners are making real progress opening up a new job-creating segment of the economy that will allow NASA to focus on our next big challenges — missions to asteroids and Mars."

Think about it: We have to build multiple homes in our solar system at some point, or else there will have to come a time when we simply take our place among the extinct.

For the moment, we inhabit a stirring, surging, moving, living planet. Earth is simply the spaceship where we see the beginning of life, its present ... and its end. Our spaceship’s bounty is finite. Its supply of energy, foodstuffs, clean atmosphere and pristine water will sooner or later be depleted.

As NASA enters 2012 with our astronauts’ launch pads dormant, we have a choice. We can just go with the flow, and slouch down the road that the dinosaurs took. Or NASA can stop its incessant drifting, and move forward with its partners to build the heavy-lift and deep-flight spaceships that will eventually make Mars the second-safest place for humans in the solar system.

'One Cannot Live in the Cradle Forever': An excerpt from 'Moon Shot'

One should read the words written more than a century ago by Russian scientist and schoolteacher Konstantin E. Tsiolkovsky. He was the first person to envision the use of rockets for space travel. In a simple but wonderful turn of words, Tsiolkovsky surveyed the future and saw what the human race must do and where it must go.

"Earth is the cradle of the mind," wrote the self-taught man who reached for tomorrow, "but one cannot live in the cradle forever."

If Tsiolkovsky is correct, and he surely must be, then let it be written that Alan Shepard and Neil Armstrong and their fellow moonwalkers took the first faltering steps from the cradle, knowing their planet one day would pass into history.

If humans were successful in journeying to Mars and populating other planets, then the human race would not be without a future. A star might go nova and obliterate an entire solar system, disease, drought, and parched lands might sweep Earth, but if humans populate other solar systems ... then life will go on.

The great storyteller Ray Bradbury, who spun tales about attempts to colonize Mars in "The Martian Chronicles," wrote: "We are all ... children of this universe. Not just Earth, or Mars, or this system, but the whole grand fireworks."

We invite you to join us in the new year for "Getting to Mars," a new series of reports about the future of Red Planet missions and the prospects for making Mars our second planetary home. It just might be the 21st century's promised land.

We are headed to Mars ... eventually. But first we need the rocket technology and human spaceflight savvy to get us there safely and efficiently. And the best way to do that is to visit places such as asteroids, our moon, a Martian moon and even no man's lands in space called "Lagrange points," NASA administrator Charles Bolden explained during the unveiling of the agency's revised vision for space exploration.

The vision shifts focus away from a return to the moon as part of a steppingstone to Mars in favor of what experts call a "flexible path" to space exploration, pushing humans ever deeper into the cosmos.

Click the "Next" label to check out six other potential destinations astronauts may visit in the years and decades to come en route to Mars.

— John Roach, msnbc.com contributor

Lessons to learn on the space station

NASA

The cooperation required to build and maintain the International Space Station will be a key to propelling humans on to Mars, according to Louis Friedman, co-founder of The Planetary Society. The society is a space advocacy organization that supports the flexible path to space exploration. In fact, the space station itself could be a training ground for Mars-bound astronauts.

Astronauts can spend ever longer blocks of time on the station to gain experience in long-duration flights, for example. They could also practice extravehicular activities akin to those expected on a Mars mission, Friedman noted.

Lunar orbit, too, is a familiar destination for human spaceflight, but a return to the familiar with new technology would allow astronauts to test the engineering of systems designed to go deeper into space, according to Friedman.

A return to the moon is still in the cards on the flexible path, but going to lunar orbit first defers the cost of developing the landing and surface systems needed to get in and out of the lunar gravity well, according to experts.

The famous "Earthrise" image shown here was made in 1968 during Apollo 8, the first human voyage to orbit the moon.

Stable no man's lands in space

NASA / WMAP Science Team

There are places in space where the gravitational pulls of Earth and the moon, or Earth and the sun, have a balancing effect on a third body in orbit. Those five locations, known as Lagrange points, could offer relatively stable parking spots for astronomical facilities such as space telescopes or satellites. Human spaceflights to these points would allow astronauts to service these instruments.

In addition, space experts believe a trip to a Lagrange point could serve as a training mission for astronauts headed to points deeper in space, such as an asteroid. Nevertheless, reaching a Lagrange point would be more of a technical achievement than a scientific achievement, according to Friedman. "It is an empty spot in space," he said.

Visit an asteroid near you?

Dan Durda
/
FIAAA

The first stop astronauts may make in interplanetary space is one of the asteroids that cross near Earth's orbit. Scientists have a keen interest in the space rocks because of the threat that one of them could strike Earth with devastating consequences. An asteroid mission would allow scientists to better understand what makes the rocks tick, and thus how to best divert one that threatens to smack our planet.

Humans have also never been to an asteroid, which would make such a visit an exciting first, noted Friedman. "Imagine how interesting it will be to see an astronaut step out of a spacecraft and down onto an asteroid and perform scientific experiments," he said. What's more, since asteroids have almost no gravity, an asteroid encounter would be like docking with the space station, which doesn't require a heavy-lift rocket for the return. That makes an asteroid a potentially less expensive destination than the surface of the moon.

The moon-Mars path of human space exploration originally envisioned the moon as a training ground for a mission to the Red Planet. While the flexible-path strategy broadens the training field, the moon remains a candidate destination, according to NASA.

Several other nations also have the moon's surface in their sights, including Japan, India and China. Some experts fear the dedicated lunar programs of these nations will eventually leave the United States in the dust as it focuses on an ambiguous flexible path.

Friedman, of The Planetary Society, said NASA should support the lunar programs of Japan, India and China as part of team building for an international Mars mission, but sees no reason for NASA to focus on the moon. "We've done that already and that was Apollo," he said.

Martian moon a final pit stop?

NASA / JPL-Caltech / UA

Before astronauts go all the way to Mars, there's reason to make a final stop at one of its moons, Phobos or Deimos. The two moons are less than 20 miles across at their widest, which means landing on them would be less expensive than the Red Planet itself.

Friedman used to consider a mission to a Martian moon nonsensical - akin to going to the base camp of Mount Everest instead of going to the top of the mountain. "I've now turned myself around on that, because you do go to the base camp and you do actually conduct training activities there before you attempt the summit," he said.

"By all means go there," he added. "Test out your rendezvous and docking at Mars, conduct your three-year, round-trip mission, maybe tele-operate some rovers of the surface (of Mars). That will all be interesting and then the next mission will finally go down to the surface."

The face of Mars

The Hubble Space Telescope focuses on the full disk of Mars, with a head-on view of a dark feature known as Syrtis Major. Hubble astronomers could make out features as small as 12 miles wide.
(AURA / STSCI / NASA)
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Red, white and blue planet

Two decades before Pathfinder, the Viking 1 lander sent back America's first pictures from the Martian surface. This 1976 picture shows off the lander's U.S. flag and a Bicentennial logo as well as the planet's landscape.
(NASA)
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Grand canyon

This is a composite of Viking orbiter images that shows the Valles Marineris canyon system. The entire system measures more than 1,875 miles long and has an average depth of 5 miles.
(NASA)
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Red rover

A mosaic of eight pictures shows the Pathfinder probe's Sojourner rover just after it rolled off its ramp. At lower right you can see one of the airbags that cushioned Pathfinder's landing on July 4, 1997.
(NASA)
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Twin Peaks at their peak

The Pathfinder probe focuses on Twin Peaks, two hills of modest height on the Martian horizon. Each peak rises about 100 feet above the surrounding rock-littered terrain.
(NASA)
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Blue horizon

A Martian sunset reverses the colors you'd expect on Earth: Most of the sky is colored by reddish dust hanging in the atmosphere, but the scattering of light creates a blue halo around the sun itself.
(NASA / JPL)
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Two-faced Mars

The image at left, captured by a Viking orbiter in the 1970s, sparked speculation that Martians had constructed a facelike monument peering into space. But the sharper image at right, sent back in 1998 by Mars Global Surveyor, spoiled the effect.
(NASA)
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A monster of a mountain

Mars' highest mountain, an inactive volcano dubbed Olympus Mons, rises as high as three Everests and covers roughly the same area as the state of Arizona. Mars Global Surveyor took this wide-angle view.
(MSSS / NASA)
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From Mars with love

This valentine from Mars, as seen by Mars Global Surveyor, is actually a pit formed by a collapse within a straight-walled trough known in geological terms as a graben. The pit spans 1.4 miles at its widest point.
(MSSS / NASA)
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Sandy swirls

An image taken by Mars Global Surveyor shows a section of the northern sand dunes on Mars' surface. The dunes, composed of dark sand grains, encircle the north polar cap.
(JPL / NASA)
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Curls of clouds

Global Surveyor focuses on a storm system over Mars' north polar region. The north polar ice cap is the white feature at the top center of the frame. Clouds that appear white consist mainly of water ice. Clouds that appear orange or brown contain dust.
(MSSS / NASA)
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Swiss cheese

Global Surveyor captured images of a frost pattern at Mars' south polar ice cap that looks like Swiss cheese. The south polar cap is the only region on the Red Planet to contain such formations.
(NASA / JPL / Malin Space Science)
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Purple Planet

A false-color image from the Opportunity rover, released Feb. 9, 2004, accentuates the differences between a green-looking slab of Martian bedrock and orange-looking spheres of rock. Scientists likened the "spherules" to blueberries embedded within and scattered around muffins of bedrock. The spherules are thought to have been created by the percolation of mineral-laden water through the bedrock layers.
(NASA / JPL / Cornell University)
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Dunes of Mars

A false-color view from NASA's Opportunity rover, released Aug. 6, 2004, shows the dune field at the bottom of Endurance Crater. The bluish tint indicates the presence of hematite-containing spherules ("blueberries") that accumulate on the flat surfaces of the crater floor.
(NASA / JPL / Cornell University)
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Alien junkyard

The Opportunity rover looks at its own heat shield, which was jettisoned during the spacecraft's descent back in January 2004, on Dec. 22, 2004. The main structure from the heat shield is at left, with additional debris and the scar left by the shield's impact to the right. The shadow of the rover's observation mast is visible in the foreground.
(NASA / JPL)
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Devil on Mars

This image shows a mini-whirlwind, also known as a dust devil, scooting across the plains inside Gusev Crater on Mars, as seen from the Spirit rover's hillside vantage point on April 18, 2005.
(NASA / JPL)
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Rub al Khali

The tracks of NASA's Opportunity rover are visible in a panoramic picture of a desolate, sandy stretch of Martian terrain in Meridiani Planum, photographed in May 2005 and released by NASA on July 28. "Rub al Khali" (Arabic for "Empty Quarter") was chosen as the title of this panorama because that is the name of a similarly barren, desolate part of the Saudi Arabian desert on Earth.
(NASA / JPL / Cornell University)
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Double moons

Taking advantage of extra solar energy collected during the day, NASA's Spirit rover spent a night stargazing, photographing the two moons of Mars as they crossed the night sky. The large bright moon is Phobos; the smaller one to its left is Deimos.
(NASA / JPL / Cornell / Texas A&M)
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Mars in the round

A 360-degree panorama shows a stretched-out view of NASA's Spirit rover and its surroundings on the summit of Husband Hill, within Mars' Gusev Crater. The imagery for the panorama was acquired in August, and the picture was released on Dec. 5.
(NASA)
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Fossil delta

Scientifically, perhaps the most important result from use of the Mars Orbiter Camera on NASA's Mars Global Surveyor has been the discovery in November 2003 of a fossil delta located in a crater northeast of Holden Crater.
(NASA / JPL / MSSS)
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Underneath the ice

This view taken in January 2005 shows sharp detail of a scarp at the head of Chasma Boreale, a large trough cut by erosion into the Martian north polar cap and the layered material beneath the ice cap.
(NASA / JPL / MSSS)
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Celestial celebration

Controllers at NASA's Jet Propulsion Laboratory in Pasadena, Calif., cheer on Friday after hearing that Mars Reconnaissance Orbiter successfully made it into orbit around the Red Planet.
(Phil McCarten / Reuters)
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Editor's note:
This image contains graphic content that some viewers may find disturbing.